Are background temperature and air temperature the same?

• A. Sometimes
• B. Yes
• C. No
• D. Not sure

Answer: (C)

In infrared measurements, air temperature and background temperature are not the same thing. Air temperature is simply how hot or cold the surrounding gas is and it mainly affects how heat is transferred to or from a surface through convection. Background temperature, on the other hand, is the temperature of the surroundings that can emit or reflect infrared energy into the camera’s view—the walls, equipment, and other objects in the scene. Since the camera detects both the object’s emitted radiation and any reflected radiation from the background, the background temperature can influence what you see even if the air temperature is different. For example, a hot surface in a cool room can still appear influenced by the warmer surroundings if those surroundings reflect IR energy toward the camera. So they are different; the background temperature is not the same as the air temperature.